fix a wrong usage of _getExplanationCache().

git-svn-id: https://svn.erp5.org/repos/public/erp5/sandbox/amount_generator@37062 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5/Document/BusinessProcess.py

@@ -187,7 +187,7 @@ class BusinessProcess(Path, XMLObject):
     if not reference_date_method_id:
       raise ValueError('a reference date method must be defined on every Trade Model Path')
 
-    explanation_cache = _getExplanationCache(self, explanation)
+    explanation_cache = _getExplanationCache(explanation)
     reference_date = explanation_cache.getReferenceDate(self, trade_date, reference_date_method_id)
 
     # Computer start_date and stop_date (XXX-JPS this could be cached and accelerated)